/**
 * @license
 * Copyright (c) 2013, Brandon Jones, Colin MacKenzie IV. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

import { GLMAT_ARRAY_TYPE } from './common';

/**
 * @class 2x2 Matrix
 * @name mat2
 */

var mat2 = {};

/**
 * Creates a new identity mat2
 *
 * @returns {mat2} a new 2x2 matrix
 */
mat2.create = function() {
    var out = new GLMAT_ARRAY_TYPE(4);
    out[0] = 1;
    out[1] = 0;
    out[2] = 0;
    out[3] = 1;
    return out;
};

/**
 * Creates a new mat2 initialized with values from an existing matrix
 *
 * @param {mat2} a matrix to clone
 * @returns {mat2} a new 2x2 matrix
 */
mat2.clone = function(a) {
    var out = new GLMAT_ARRAY_TYPE(4);
    out[0] = a[0];
    out[1] = a[1];
    out[2] = a[2];
    out[3] = a[3];
    return out;
};

/**
 * Copy the values from one mat2 to another
 *
 * @param {mat2} out the receiving matrix
 * @param {mat2} a the source matrix
 * @returns {mat2} out
 */
mat2.copy = function(out, a) {
    out[0] = a[0];
    out[1] = a[1];
    out[2] = a[2];
    out[3] = a[3];
    return out;
};

/**
 * Set a mat2 to the identity matrix
 *
 * @param {mat2} out the receiving matrix
 * @returns {mat2} out
 */
mat2.identity = function(out) {
    out[0] = 1;
    out[1] = 0;
    out[2] = 0;
    out[3] = 1;
    return out;
};

/**
 * Transpose the values of a mat2
 *
 * @param {mat2} out the receiving matrix
 * @param {mat2} a the source matrix
 * @returns {mat2} out
 */
mat2.transpose = function(out, a) {
    // If we are transposing ourselves we can skip a few steps but have to cache some values
    if (out === a) {
        var a1 = a[1];
        out[1] = a[2];
        out[2] = a1;
    } else {
        out[0] = a[0];
        out[1] = a[2];
        out[2] = a[1];
        out[3] = a[3];
    }

    return out;
};

/**
 * Inverts a mat2
 *
 * @param {mat2} out the receiving matrix
 * @param {mat2} a the source matrix
 * @returns {mat2} out
 */
mat2.invert = function(out, a) {
    var a0 = a[0], a1 = a[1], a2 = a[2], a3 = a[3],

        // Calculate the determinant
        det = a0 * a3 - a2 * a1;

    if (!det) {
        return null;
    }
    det = 1.0 / det;

    out[0] =  a3 * det;
    out[1] = -a1 * det;
    out[2] = -a2 * det;
    out[3] =  a0 * det;

    return out;
};

/**
 * Calculates the adjugate of a mat2
 *
 * @param {mat2} out the receiving matrix
 * @param {mat2} a the source matrix
 * @returns {mat2} out
 */
mat2.adjoint = function(out, a) {
    // Caching this value is nessecary if out == a
    var a0 = a[0];
    out[0] =  a[3];
    out[1] = -a[1];
    out[2] = -a[2];
    out[3] =  a0;

    return out;
};

/**
 * Calculates the determinant of a mat2
 *
 * @param {mat2} a the source matrix
 * @returns {Number} determinant of a
 */
mat2.determinant = function (a) {
    return a[0] * a[3] - a[2] * a[1];
};

/**
 * Multiplies two mat2's
 *
 * @param {mat2} out the receiving matrix
 * @param {mat2} a the first operand
 * @param {mat2} b the second operand
 * @returns {mat2} out
 */
mat2.multiply = function (out, a, b) {
    var a0 = a[0], a1 = a[1], a2 = a[2], a3 = a[3];
    var b0 = b[0], b1 = b[1], b2 = b[2], b3 = b[3];
    out[0] = a0 * b0 + a2 * b1;
    out[1] = a1 * b0 + a3 * b1;
    out[2] = a0 * b2 + a2 * b3;
    out[3] = a1 * b2 + a3 * b3;
    return out;
};

/**
 * Alias for {@link mat2.multiply}
 * @function
 */
mat2.mul = mat2.multiply;

/**
 * Rotates a mat2 by the given angle
 *
 * @param {mat2} out the receiving matrix
 * @param {mat2} a the matrix to rotate
 * @param {Number} rad the angle to rotate the matrix by
 * @returns {mat2} out
 */
mat2.rotate = function (out, a, rad) {
    var a0 = a[0], a1 = a[1], a2 = a[2], a3 = a[3],
        s = Math.sin(rad),
        c = Math.cos(rad);
    out[0] = a0 *  c + a2 * s;
    out[1] = a1 *  c + a3 * s;
    out[2] = a0 * -s + a2 * c;
    out[3] = a1 * -s + a3 * c;
    return out;
};

/**
 * Scales the mat2 by the dimensions in the given vec2
 *
 * @param {mat2} out the receiving matrix
 * @param {mat2} a the matrix to rotate
 * @param {vec2} v the vec2 to scale the matrix by
 * @returns {mat2} out
 **/
mat2.scale = function(out, a, v) {
    var a0 = a[0], a1 = a[1], a2 = a[2], a3 = a[3],
        v0 = v[0], v1 = v[1];
    out[0] = a0 * v0;
    out[1] = a1 * v0;
    out[2] = a2 * v1;
    out[3] = a3 * v1;
    return out;
};

/**
 * Returns Frobenius norm of a mat2
 *
 * @param {mat2} a the matrix to calculate Frobenius norm of
 * @returns {Number} Frobenius norm
 */
mat2.frob = function (a) {
    return(Math.sqrt(Math.pow(a[0], 2) + Math.pow(a[1], 2) + Math.pow(a[2], 2) + Math.pow(a[3], 2)))
};

/**
 * Returns L, D and U matrices (Lower triangular, Diagonal and Upper triangular) by factorizing the input matrix
 * @param {mat2} L the lower triangular matrix
 * @param {mat2} D the diagonal matrix
 * @param {mat2} U the upper triangular matrix
 * @param {mat2} a the input matrix to factorize
 */

mat2.LDU = function (L, D, U, a) {
    L[2] = a[2]/a[0];
    U[0] = a[0];
    U[1] = a[1];
    U[3] = a[3] - L[2] * U[1];
    return [L, D, U];
};


export default mat2;
